You might just try replacing the small electrolytic caps on the main board first and see if that takes care of it. If one of them is leaky it could cause a dc offset... especially on something this old. It's hard for me believe but I repaired my first Flame Linear 400 in 1973!! you may also find that you can't get the offset as low as you'd like. The model 700 had a DC offset pot... the 400 only had a bias pot if my mind is still cookin.

Agreed! However...always re-cap an amp this old first... then go from there. It does you no good to have 30 year old electrolytics in there that were originally el=cheapo 10 cent caps anyway. I remember typically <25mv when all is said and done on a properly working 400. The model 700 could do much better but had to be tweeked occasionally.

You might just try replacing the small electrolytic caps on the main board first and see if that takes care of it. If one of them is leaky it could cause a dc offset... especially on something this old. It's hard for me believe but I repaired my first Flame Linear 400 in 1973!! you may also find that you can't get the offset as low as you'd like. The model 700 had a DC offset pot... the 400 only had a bias pot if my mind is still cookin.

Any capacitor should be better than the originals correct? Like non-polarized metal film.

Let's see you try to replace the boot strap cap with one of those. Won't fit.

And the bootstrap is a little weird on this one - it connects to the driver transistor and not the output. And in that position, just a little leaky will give you a DC offset. A lot leaky, and the amp can latch up.

Let's see you try to replace the boot strap cap with one of those. Won't fit.

And the bootstrap is a little weird on this one - it connects to the driver transistor and not the output. And in that position, just a little leaky will give you a DC offset. A lot leaky, and the amp can latch up.